Fluorosilicone rubbers have excellent heat resistance, low temperature resistance, resistance to chemicals, etc., and are used in various fields. However, they have difficulties in adhesion to metal, plastic or the like, and their use for composite materials comprising combinations of fluorosilicone rubbers with metal, plastic, etc;, has been limited.
In view of the above, there have been proposed treatments of the surface of a substrate such as metal, plastic, etc., with a primer in order to attain strong adhesion of a fluorosilicone rubber or its coating to such a substrate. For those treatements, various primer compositions have been proposed.
Primer compositions of this type are known as described in, for example, JP-B-53-14580 and JP-A-59-182865. (The terms "JP-B" and "JP-A" as used herein mean an "examined Japanese patent publication" and an "unexamined published Japanese patent application", respectively.) However, in order to obtain a sufficient adhesion-improving effect of those primer compositions, a fluorosilicone rubber and a substrate treated with those primer compositions should be pressed together at a high temperature under a high pressure for a relatively long period of time, since they hardly adhere to each other if the curing is conducted by an atmospheric hot-air vulcanization. Further, those primer compositions are still insufficient in adhesive properties when used in the adhesion of fluorosilicone rubbers to plastics such as nylon and polyethylene terephthalate.